Solvent groups

Important information and data on individual solvents are listed in the following tables  

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Solvents grouped in the same region of the triangle will have similar selectivity, whereas solvents from other groups will have different selectivity even if their solvent strengths are similar. Acetone is a solvent characterized by a polarity value of 5.1 (group VI, e). Its X values given in Table 4.2 show its polar interaction properties that involve 35% proton-acceptor, 23% proton-donor, and 42% dipole interactions. Solvents near the comers have mainly one kind of selectivity. 

Visser, A. E., Swatloski, R. P, Reichert, W. M., Griffin, S. T., Rogers, R. D., Traditional extractants in nontraditional solvents Groups 1 and 2 extraction by crown ethers in room-temperature ionic liquids, Ind. Eng. Chem. Res., 39,3596-3604,2000. 

The solvents chosen, A and B, should be from two of the eight solvent groups and be as different as possible. Since it has been shown that three solvents are better than two, the ideal ternary mixture for normal phase LC should have three solvents chosen from the three apices of the triangle. 

This section deals only with solvents whose reduction products are insoluble in the presence of lithium ions. The list includes open chain ethers such as diethyl ether, dimethoxy ethane, and other polyethers of the glyme family cyclic ethers such as THF, 2Me-THF, and 1,4-dioxane cyclic ketals such as 1,3-dioxolane and 1,3-dioxane, esters such as y-butyrolactone and methyl formate and alkyl carbonates such as PC, EC, DMC, and ethylmethyl carbonate. This list excludes the esters, ethyl and methyl acetates, and diethyl carbonate, whose reduction products are soluble in them (in spite of the presence of Li ions). Solutions of solvents such as acetonitrile and dimethyl formamide are also not included in this section for the same reasons. Figure 6 presents typical steady state voltammo-grams obtained with gold, platinum, and silver electrodes in Li salt solutions in which solvent reduction products are formed and precipitate at potentials above that of lithium metal deposition. These voltammograms are typical of the above-mentioned solvent groups and are characterized by the following features ... 

The data plots of Fig. 15b (silica) are differentiated for the use of methyl- -butyl ether (MTBE) or acetonitrile (ACN) as localizing solvent C in the mobile phase. It is seen that for some solute pairs (Fig. 15a and c) the open squares (MTBE) fall on a different curve than the closed squares (ACN). This implies that the constant in Eq. (31a) is solvent-specific, rather than being constant for all solvents (as first-order theory would predict). A similar behavior is observed for alumina as well. Figure 15a plots data for 18 different polar solvents B or C, and some scatter of these plots of log a versus m is observed here, as in Fig. 15b for silica. The variation of Q with the localizing solvent C used for the mobile phase has been shown (18) to correlate with the relative basicity of the solvent, or its placement in the solvent classification scheme of Refs. 40 and 41. Thus, for relatively less basic solvents (groups VI or VII in Refs. 40 and 4/),... 

A.E. Visser, R.P. Swatloski, W.M. Reichert, S.T. Griffin, R.D. Rogers, Traditional Extractants in Nontraditional Solvents Groups 1 and 2 Extraction by Crown Ethers in Room-Temperature ionic Liquids , Ind. Eng. Chem. Res., 39, 3596 (2000)... 

The rate of Hj absorption by the group VA metals is increased by thin overlayers " of Pd or Pt Ni and Fe are less effective, and Cu and Ag have no appreciable effect, at least not with Ta. The solution of small amounts of a second metal yields alloys that react rapidly with Hj at RT without activation . The second metal should have a radius > 5% smaller than that of the solvent group VA metal, e.g., Co, Fe and Ni. 

The second solvent or modifier is then chosen from one of the remaining solvent groups. In reversed phase HPLC, this is most often one of three solvents methanol (Group II), acetonitrile (Group VI) or THF (Group III). All three of these solvents have low viscosity, a reasonably low toxicity level and a low UV cutoff and most separations can be achieved with a mixture of one or more of them with water. 

The combinatorial part In yp is calculated from pure-component properties. The residual part In yf is calculated by using binary interaction parameters for solute-solvent group pairs determined by fitting phase equilibrium data. Both parts are based on the UNIQUAC set... 

Robbins Chart of Solute/Solvent Group Interactions... 

The Robbins Chart of Solute/Solvent Group Interactions, shown in Table 11.2, is useful in selecting the appropriate solvent type for a given phytochemical. This chart helps quantify the old adage that like dissolves like and provides a system for choosing a solvent for a given solute, based on their respective chemical... 

Fig. 4.4 Plot of the stickiness parameter to against the values of fip /(eod ), which characterizes the strength of dipole-dipole interactions for two selected solvent groups.

The total potential energy of the system, C/T, partitioned into quantum (solute) and molecular mechanics (solvent) groups of atoms is given by... 

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